1. Field of the Invention
The present invention relates to a surface emitting laser array, a production process thereof, and an image forming apparatus having a surface emitting laser array.
2. Description of the Related Art
A vertical cavity surface emitting laser (VCSEL) is a laser capable of emitting light in a direction perpendicular to a substrate surface and has a feature that a two-dimensional array can be easily formed, which an edge-emitting type laser does not have.
In particular, densification and faster operation can be simultaneously achieved by the parallel processing of multiple beams emitted from the two-dimensional array, and so it is expected to be used in various industrial applications. For example, when a vertical cavity surface emitting laser array is used as a light source for exposure of electrophotography, high-definition and faster printing can be achieved by parallel processing in a printing process by utilizing multiple beams.
On the other hand, the vertical cavity surface emitting laser involves a problem that saturation of light output is caused by temperature rise caused by generation of heat upon low-current driving compared with the edge-emitting type laser, and so the light output is limited.
In addition, the vertical cavity surface emitting laser also involves a problem that light output is lowered with rise of a peripheral temperature (environmental temperature) of a device.
In order to solve such problems, Japanese Patent Application Laid-Open No. 2003-086895 has proposed a vertical cavity type semiconductor light-emitting device in which a peripheral part of a mesa structure is charged with a plated metal to dissipate heat as well as to impart a function as an electrode.
When an array type vertical cavity surface emitting laser is applied to a light source for electrophotography, the distance between vertical cavity surface emitting laser devices is more and more shortened from demands such as faster operation and high definition, and there is a demand for more narrowing the pitch between the devices.
When peripheral parts of a mesa structure of such a narrow-pitch laser are charged with a plated metal like Japanese Patent Application Laid-Open No. 2003-086895, thereby forming plated structures which take a radiator function as a heat sink part, the plated structures come into contact with each other, so that the devices are difficult to be independently driven.
On the other hand, in order to independently drive the devices, it is also considered that a plating-formation-inhibiting portion is formed as a device-isolating structure between the narrow-pitch devices. When such a device-isolating structure is formed, however, it is difficult to allow the area of the plated structure having the radiator function to be large.
As described above, it is difficult to achieve both independent drive of the respective devices and efficient heat dissipation when the distance between the devices is narrow in the prior art.